Limitations
Following are the Limitations:
-
SR/ICSR is not supported for this feature.
-
Restarting trace immediately after quitting may result in fastpath files in
/records/pcap
directory to be overwritten. We recommend you to restart the session after a brief moment (a few seconds). -
When MonSub trace is stopped, the tear down process can take a few seconds, so it is recommended to wait for few seconds. A maximum of (5 sec, hexdump poll timer value in sec) before toggling the MonSub trace to start, else operators may observe MAX TRACING SESSIONS REACHED momentarily.
-
Show monitor subscriber fastpath sessions CLI does not display the MonSub sessions that are being stopped. Hence there is a transient period where new MonSub sessions can be rejected due to max sessions reached, whereas show CLI shows fewer sessions. We recommend you to wait for some time before starting a new MonSub trace session.
-
Changing fastpath configuration options is only possible when UP Pcap Trace is set to OFF.
-
When MT=ON in the Multi-PDN, then once MT=OFF, new PDN tracing is not started due to MAX TRACING REACHED, and then all other tracing is STOPPED. This is because the first new PDN tracing is started and then all previous PDNs were STOPPED for MT=OFF case.
-
We recommend not to launch the same UE MonSub sessions from different CLIs.
-
In slowpath PCAP, the egress DL packets do not show the GTPU-U header because the functionality to add GTP-U is with fastpath. So, ingress and egress DL packets shows up the duplicates, unless there is some packet modification like HTTP X-headers applied over the ingress packets.
-
Toggling C and D options does not impact the PCAP captures in UPF.
-
For Multi-PDN, the fastpath filenames do not use the Call ID, because, by definition the multi-PDN case has more than one call ID and hence a higher-level configuration such as IMSI is more suitable for naming the files.
-
Only the named options that are explicitly mentioned in this document are supported from hexdump-module file configuration.
-
Number of streams that can be traced in fastpath is limited to 5000. Stream is defined as a TCP or UDP flow which is made up of {source IP address, destination IP address, source port, and destination port, transport protocol such as TCP or UDP).
-
Fastpath packets cannot be streamed to an external server. They are stored on the hard-disk and transferred (either manually) or by using transfer-mode options.
-
The UP PCAP trace must be set to ON to capture fastpath and slowpath PCAP files.
-
MonSub CLI option ‘<SPACE> Pause’ is only to pause console events. There is no impact on other tracing events (slowpath PCAP, fastpath PCAP and protocol packets tracing in a text file in hexdump format) with this option.
-
The UP trace PCAP file does not contain the initial PFCP Sx Request/Response, due to race condition.
-
The ICMP Packets and first packets of TCP and UDP streams flow through both slowpath and fastpath. Default values of GTPU (option 26) and User L3 (Option 19) are set to OFF. As a result, these packets are not captured in slowpath captures. If Option 26 is set to ON, then these packets are captured in slowpath PCAP captures. As mentioned in previous point, option 19 has no effect on slowpath PCAP capture.
-
Data Events flag must be set to ON to capture fastpath and slowpath PCAP files.
-
The Mon sub tracing is not supported for option Next-SAEGW Call on UP.
-
The Mon sub tracing is not supported for option Next call by APN for Pure-S call type.
-
On ASR-5500 setup with the default value of poll-timer, all the packets may not be captured due to a known issue. To avoid large number of packets to be rejected, we recommend you to change the poll-timer value to the lowest possible (10 ms).
-
If context replacement occurs (if the same subscriber reattaches without a detach), then the slowpath captures for the new call remain in the old slowpath files.